Perhaps we also need a dual index that measures how well a pigment retains the same appearance under various light sources.
Synthetic and natural dye will degrade or "patina" in different ways, over time and over the course of exposure to weathering, UV light, etc.
In many cases the synthetic dye does not degrade at all, which for many use cases can be undesirable.
My thinking is this could affect visual cues for e.g. training.
Visualization of this: https://imgr.search.brave.com/OsaL9Hps1NYNjbK4zhGnStZmlMNT3t...
Human sight reduces all visible light down to the three red/green/blue buckets. Other species will have different buckets, and can easily see colors we perceive as identical as completely different.
I believe we have better color vision that most animals though, so the opposite is usually the case.
EDIT: Here's the reported anecdote I was remembering:
> "I have always had polite disagreements with people about shades of colours," she says. When clothes shopping for instance, she often finds that apparently matching tops and skirts seem to be a different shade to her, clashing horribly--even though no one else seems to notice it. Her sensitivity can sometimes be baffling to those around: when helping to restore a house, she once rejected 32 paint samples before settling on the right shade. "The beiges were too yellow and not blue enough, not cool enough; some of the almonds were too orangey," she says--distinctions that were much to the confusion of her building contractor.
https://www.bbc.com/future/article/20140905-the-women-with-s...
Another species could have the exact same "buckets" configuration and perceive color differently if the ganglionic layer is connected differently to those buckets.
But if you look at infrared photos of flowers or "how bees see them", they show the same flowers with landing strips for the bees.
I can see how that would actually make it look better/different in non full spectrum light!
But I don't get how pre tech dye experts would pick such colors?